To prevent a device from being detached by an action such as vibration by surely mounting a cover body on a case body in a harness case comprising the case body and the cover body.

The cover body 3 is foldably connected to the case body 2 via a flexible connecting part b in one side part in the longitudinal direction, so that a storage part a of the harness H is opened and foldably closed to the case body 2. A stacked part c is formed by stacking a projecting piece 2B of the case body 2 with a projecting piece 3B of the cover body 3 when folding the cover body 3 so that, when the harness case 1 is mounted on a mount part 50 by a mount means 4A via the stacking part c, the mounting on the case body 2 in folding the cover body 3 is simultaneously performed by the mount means 4A.